**2. Materials and methods**

*Protected Areas, National Parks and Sustainable Future*

or at least mitigate losses in pine ecosystems.

pine as a foundation species because it provides locally stable conditions needed by several co-occurring species. Its loss thus alters several ecosystem processes such as forest productivity and hydrology [6]. According to Tomback and Achuff [5], without active management, many pine-associated communities may disappear and their loss would result in severe impacts to biodiversity and other ecosystem services. They recommend using timely proactive restoration programmes to avoid

In eastern North America, the eastern white pine (*Pinus strobus* L.) was also much more prevalent in pre-settlement forests than it is today [7–9]. Eastern white pine is the tallest tree in eastern North America and ecologically typifies the northern forests of eastern United States [10]. This noble tree species has been important for economic, social, and cultural reasons [11]. As western white pines, it has been also severely impacted by the exotic white pine blister rust, *Cronartium ribicola* J.C. Fisch [12]. Moreover, fire suppression policies have altered the natural dynamics of eastern white pine stands by allowing shade-tolerant species, such as balsam fir (*Abies balsamea* L.), to outcompete pine seedlings [8, 10, 13–15]. Finally, selective logging of mature eastern white pines during the eighteenth and nineteenth centuries has reduced seed tree density and, thus, its regeneration potential [16, 17]. Historically, eastern white pine regeneration was favoured by surface fires, which improve seedbed quality, increase light availability, and reduce competition from saplings of other shade-tolerant tree species [7, 14, 18]. Mature eastern white pines survive most surface fires due to their thick bark [19], branch-free lower trunks, and deep roots [20]. Their needles have a low content of resin and thus are not highly flammable [21]. Eastern white pine reaches the northern limit of its range in the southern part of eastern Canada, where most ignitions are rapidly suppressed for safety reasons. Other than fire, the natural regeneration dynamics of eastern white pine in old stands is still poorly understood, mainly at the northern limit of its range [11]. Recent studies have recognized the importance of gap dynamics, which is closely related to understory light for seedlings [22, 23]. Uprety et al. [11] concluded that management strategies should be different near the northern range limits because site conditions and disturbances have different effects than in the centre of a species' range. Regenerating eastern white pine thus remains an important challenge and researchers still test methods to reduce the effect of competing vegetation [24]. However, this mainly involves using herbicides [24] or thinning

[25], approaches not compatible with the mandate of national parks.

The *Canada National Parks Act* requires maintaining or restoring the ecological integrity of the parks through the protection of natural resources and ecological processes. Ecological integrity is defined as 'a condition that is determined to be characteristic of its natural region and likely to persist, including abiotic components and the composition and abundance of native species and biological communities, rates of change and supporting processes' [26]. Because several parks have been established in areas previously disturbed by logging, Parks Canada often needs to develop management approaches to restore these ecosystems to make them sustainable for future. The objective of restoring the ecological integrity of eastern white pine forest ecosystems to pre-settlement conditions, or at least within their historic range of variability [27, 28], might be achieved by using prescribed burning as a management approach [29, 30]. In the context of a national park, prescribed burning represents a tool for reintroducing a natural ecological process. Prescribed burning has been shown to promote regeneration of several fire-favoured pine species, such as *P. ponderosa*, *P. pungens*, and *P. rigida* [31–34], but its efficacy remains to be demonstrated in eastern white pine forests. In La Mauricie National Park of Canada, eastern white pine proportion was estimated at 5–12% in pre-settlement forests but now represents only 0.5% of the current forest composition. Meanwhile, balsam fir has increased from 13.1 to 31.8% [35–37].

**40**

## **2.1 Study area, stand selection, and burn treatment**

The study was carried out in La Mauricie National Park of Canada (**Figure 1**), which is located in Quebec, Canada. The park was established in 1977 and covers 536 km2 . It belongs to the sugar maple-yellow birch bioclimatic domain and is a typical Laurentian Mountains landscape moulded with hills and lakes. Annual precipitations vary between 900 and 1400 mm and annual mean temperatures vary between 2.5 and 5.0°C [39]. Seven stands treated with prescribed burning between 1995 and 2005, and nine unburned stands, were selected over an area of 40 km<sup>2</sup> . The altitude of the 16 selected stands ranged between 217 and 341 m and their slope varied between 1 and 47% (**Table 1**).

Prescribed burning was used in stands where eastern white pine density was >15 trees/ha, the slope <50%, and balsam fir saplings dominated the understory. In these sites, eastern white pine seedling and sapling densities were considered too

#### *Protected Areas, National Parks and Sustainable Future*


#### **Table 1.**

*Description of the 16 sites studied at La Mauricie National Park of Canada.*

#### **Figure 2.**

*Parks Canada crew using a driptorch to run a prescribed burning experiment in a white pine stand at La Mauricie National Park of Canada.*

low to ensure eastern white pine renewal, thus preventing the park from reaching its objective of maintaining or restoring ecological integrity [40]. Burning prescriptions were defined using the Canadian Forest Fire Danger Rating System [41] and the software FBP97 for forecasting fire behaviour [42]. Prescribed burnings were carried out during spring because burning conditions are more suitable before bud flushing of broadleaved trees and shrubs [43]. When conditions were appropriate, fire was ignited using burners (driptorch; **Figure 2**) or a helicopter equipped with a Premo MK3 aerial ignition device. Low-intensity surface fires were isolated and controlled with natural and artificial firebreaks. Flame height and length were recorded during each prescribed burning event by the park's staff and were used to estimate fire intensity based on the Canadian forest fire behaviour prediction system [41] (**Table 1**). For low-intensity surface fires, these classes range from 1 (frontal fire intensity < 10 kW/m; flame length < 0.2 m; flame height < 0.1 m) to 5 (frontal fire intensity > 4000 kW/m; flame length >3.5 m; flame height >2.5 m). In our study, fire intensity in burned sites mostly belongs to class

**43**

**3. Results**

*Prescribed Burning to Restore Eastern White Pine Forests of La Mauricie National Park…*

3 (frontal fire intensity: 500–2000 kW/m; flame length: 1.4–2.6 m; flame height: 1.0–1.9 m). However, fire intensity reached class 4 in the stand burned in 1999 (frontal fire intensity: 2000–4000 kW/m; flame length: 2.6–3.5 m; flame height: 1.9–2.5 m) and killed many mature trees including some eastern white pines.

distance of 50 m from stand or treatment edges were set up in each stand to describe the forest environment. In each plot, we recorded the slope (%), altitude (m), surface deposit, drainage, and thickness of the soil organic layer (litter and humus) (**Table 1**). Species, diameter at breast height (hereafter DBH), and decay class of each standing tree or snag ≥9.1 cm at DBH were recorded. Decay classes were determined according to Hunter classification [44], which recognizes nine classes for trees (1: alive and 2: declining) and snags (3: dead tree with bark intact up to 9: stump). Because most pines were large and tall, their density was rather low and, to get more accurate estimates of their basal area, we enlarged the sampled plots

at 8.46 m from the plot centre, in each cardinal direction. Saplings and seedlings

trees in which DBH ranged between 1 and 9 cm, whereas seedlings were very young trees with DBH smaller than 1 cm [45]. Sapling DBH was measured and seedling height was recorded into 5-cm classes. Eastern white pine relative dominance was

As stands had not been sampled before treatment, the short-term effects of prescribed burning were assessed using the percentage of recent tree or sapling mortality in 1- to 7-year-old burns (older burns could not represent short-term effects of prescribed burning) and compared to unburned stands. Tree BA and sapling density (stems/ha) were calculated for eastern white pine, balsam fir, spruces, and broadleaved species. Then, the percentages of recent mortality (Hunter classes 3 and 4) were calculated for both burned and unburned stands. Student's *t*-tests were used to compare recent mortality of trees and saplings in both stand types. We also used Student's *t*-tests to compare seedling density in burned and unburned stands. Sites burned in 2004 and 2005 were excluded from the seedling analysis because no seed crop had occurred after the treatment, thus precluding the establishment of regeneration in these stands. Logarithmic transformations (log x + 1) were used to normalize the distributions and stabilize variances when necessary. When transformations did not achieve equality of variances, we used results obtained with Satterthwaite's approximate *t*-test, a method that belongs to the Behrens-Welch

(radius = 19.55 m). In each 400-m2

estimated on the basis of its relative basal area (hereafter BA, in m2

plots, in relation to BA of other tree species estimated in the 400-m2

family [46]. Analyses were performed using SAS software v. 9.1. [47].

Forest composition of unburned stands was dominated by conifers, with slightly

more than 75% of the tree basal area belonging to eastern white pine and other conifers, mostly spruces (**Table 2**). Balsam fir represented less than 10% of tree basal area, and broadleaved trees slightly more than 15%. Prescribed burnings significantly

(radius = 2.82 m) and four micro plots of 4 m2

were recorded in the 25 and 4-m2

**2.3 Statistical analysis**

circular plots located 50 m apart along a transect and at a minimum

plot, four smaller plots of 25 m2

/ha) in 1200-m<sup>2</sup>

plots.

(radius = 1.13 m) were established

plots, respectively. Saplings were defined as young

*DOI: http://dx.doi.org/10.5772/intechopen.86224*

**2.2 Forest inventory**

Three 400-m2

up to 1200 m<sup>2</sup>

3 (frontal fire intensity: 500–2000 kW/m; flame length: 1.4–2.6 m; flame height: 1.0–1.9 m). However, fire intensity reached class 4 in the stand burned in 1999 (frontal fire intensity: 2000–4000 kW/m; flame length: 2.6–3.5 m; flame height: 1.9–2.5 m) and killed many mature trees including some eastern white pines.
